The present invention is generally directed to adapters and disposable liners for centrifuge containers. More particularly, this invention is directed to adapters and liners that localize pellet formation, thus increasing the recovery of pelleted material.
Centrifugation is a widely used method for separating solid and liquid phases of suspensions. The solid phase is more dense than the liquid phase, and during centrifugation, solids settle at the bottom of the centrifuge container, forming a dense pellet. The lighter liquid phase forms a top layer, also called a supernatant. At the end of centrifugation, the supernatant can be decanted and the pellet harvested or discarded. The initial separation step may be followed by wash steps. During a wash step, the pellet is resuspended in a wash liquid. The resuspended solid component then may be pelleted once again by means of centrifugation and the supernatant wash liquid decanted from the container. In certain applications, this step can be repeated several times with the same or a different wash liquid.
Currently, tube-carrying rotors, as well as bowl-type centrifuge rotors, are available on the market. The following discussion is limited to tube-carrying rotors of which there are three main types: swinging bucket rotors, fixed angle rotors, and vertical tube rotors. All three types of tube-carrying rotors include a plurality of symmetrically located cavities, adapted to receive sample containers. Sample containers for centrifugation are manufactured in a variety of sizes, materials, wall thicknesses, and sealing means to accommodate chemically and pathogenically active samples and a wide range of operating conditions.
The existing designs of centrifuge containers, however, do not offer an easy access to pellets for their harvesting or disposal. In some applications, sample containers have to be cut to retrieve a pellet, which is not always an economically feasible option. In applications dealing with diluted suspensions, such as cell cultures, forming a concentrated pellet, by itself, can be a difficult task, let alone harvesting of such a small pellet from conventional centrifuge containers. In such samples, as a result of centrifugation, a very thin layer of solids becomes spread over a large surface of the container. In order to recover the pellet, it has to be scraped from the walls of the container, leaving some pelleted materials behind. Such a procedure reduces the percentage of pelleted material recovery and increases the chance of cross-contamination. Furthermore, the container would then need to be washed and autoclaved for the next run.
Cleaning of the centrifuge containers from the solids remaining on the walls after the pellet is harvested requires laborious and tedious scrubbing and washing. The difficulty of thorough cleaning of the centrifuge container further increases as the dimensions of the neck opening of the container decreases. That is, whereas some types of solid residue may be easily cleaned from wide-mouthed bottles, such residue becomes more difficult to remove where the bottle is of narrow-mouthed construction.
The manufacturing of conventional centrifuge containers requires that materials are selected according to their structural strength and fatigue resistance, and not necessarily for their chemical or sterilization resistance. However, the mechanical strength of the materials does not always correspond to their chemical and physical resistance. Consequently, certain chemically aggressive materials cannot be processed in conventional centrifuge containers or require bulky and expensive designs.
Conventional centrifuge containers cannot accommodate applications where the pellet is a hazardous material (e.g., a biohazard) and a minimal direct handling of the pellet by a technician is desirable. Also, when an aseptic procedure is called for, the centrifuge containers have to be sterilized, which often takes 30-60 minutes. This relatively long preparation time of a conventional centrifuge container further decreases efficiency of the sample processing.
The conventional centrifuge container designs, therefore, fail to provide convenient methods for precipitating solids into small, concentrated pellets by centrifugation and their efficient recovery. They also do not accommodate aseptic harvesting of suspended solids by centrifugation with little or no time required for cleaning and sterilization of the containers prior to the next centrifugal cycle.
Accordingly, it is an object of the present invention to develop a cost-efficient, rapid and convenient method for the separation of the solids from suspensions by centrifugation. Particularly, it is an object of the present invention to develop a centrifuge container adapter that allows efficiently collected solids from suspensions by forming localized, concentrated pellets. It is also an object of the present invention to provide an assembly of the centrifuge container adapter and a liner that minimizes the time required for cleaning of the centrifuge container, reduces direct exposure of a technician to hazardous pellets and, at the same time, increases the efficiency of the pellet harvesting.
These and other objects and advantages are achieved in the adapter of the present invention having a hollow body with an opening on top, an exterior surface and an interior surface. The adapter is designed for placement inside a cavity of a centrifuge container. Typically, centrifuge container cavities have a closed bottom portion and an open upper portion. The exterior surface of the adapter body completely conforms to the bottom portion of the centrifuge container cavity. The interior surface of the adapter body has an internal sidewall and a bottom with a pellet well. The pellet well extends downwardly, toward the exterior surface.
In one embodiment, a portion of the internal sidewall tapers toward the pellet well. Alternatively, the entire interior surface of the adapter may taper from the adapter opening toward the pellet well. In one embodiment, the interior surfaces comprise a plurality of cylindrical and conical internal sidewalls, formed one on top of the other and having different or the same tapers.
The size of the well may be varied to accommodate different concentrations of the suspended solid materials. Preferably, the capacity of the well should be sufficient to harvest substantially all suspended solids.
In another aspect, the present invention provides an assembly for use with a centrifuge container. The assembly includes the adapter of the present invention described above and a liner, conforming to the interior surface of the adapter, once inside the adapter. In the preferred embodiment, the liner has a height equal or larger than the depth of the interior of the adapter body.
The present invention also overcomes deficiencies of the prior techniques by providing a novel method for separating the solids from suspensions by utilizing the adapter of the instant invention. In this method, the removable adapter with a pellet well of the present invention is placed into a centrifuge container. Then, the suspension is placed into the centrifuge container. When centrifugation is completed, the pellet is removed from the pellet well. The method may include an additional step of placing a liner conforming to the interior of the adapter into the adapter prior to placing the suspension into the centrifuge container. The liner is removed from the container with the pelleted solids contained in the bottom portion of the liner. The pelleted solids on the liner may be either harvested or discarded.
The present invention has been found to provide a number of advantages. The adapter with a pellet well for centrifuge container can be used to recover the solids from a broad range of suspensions, which includes, but is not limited to, biological materials, such as cell lysates, blood, urine, and culture media. The invention is particularly advantageous in applications dealing with the recovery of solids from diluted samples, as it allows the concentration of the solids into a compact pellet. In contrast, the centrifugation of suspensions with a low concentration of suspended solids in conventional centrifuge containers leads to spreading of a very thin layer of the solids over a large surface of the centrifuge container, making the harvesting of the solids hard, if not impossible.
The adapter of the present invention can be designed to fit a wide variety of centrifuge containers, including, but not limited to, centrifuge containers used in a swinging bucket, vertical tube, and fixed angle rotors. For additional convenience, an assembly of the adapter of the present invention with a liner conforming to the interior of the adapter may be used. The liner of this invention can be made disposable, which eliminates the need for the mechanical cleaning of the centrifuge container and the adapter. The disposable liners can be sterilized to accommodate the aseptic sample processing.
The present invention is defined in its fullest scope in the appended claims and is described below in its preferred embodiments.